Urban areas in Taiwan frequently experience unhealthy levels of particulate, ozone, and carbon monoxide. The Taiwan Environmental Protection Administration, formed in 1987, has begun an aggressive program to improve air quality by addressing all major sources of air pollution. Mobile emissions sources are responsible for over 90 percent of CO, NOx, and HC emissions in the Taipei area. New emissions standards for light-duty vehicles and motorcycles took effect in 1990 and 1991, respectively; these standards are expected to significantly reduce emissions from these vehicle classes as the new models are phased into the vehicle population. However, additional reductions may be needed in Taipei and other urban areas.Alternative fuels-including liquefied petroleum gas (LPG), natural gas, methanol, ethanol, and electricity-represent a promising strategy for achieving these reductions. Vehicle technology for these fuels is being developed rapidly throughout the world. However, limited work is being done on motorcycles, which represent a large part of Taiwan's emissions inventory. Significant amounts of LPG and natural gas may be available in Taiwan for vehicular use within the next ten years. The Taipei taxi fleet is a potential initial market for use of LPG or another alternative fuel.